The HTTP range request header may be used to request specific parts of a resource.
A server may specify to clients that the range header is supported by adding the accept-ranges to the response headers, this is done like this:
HTTP/1.1 200 Ok accept-ranges: bytes
It can be useful when supporting streaming of multimedia files, and when sending large downloads over the HTTP protocol.
Servers should support the range header out-of-the-box for static files, but if you wish to support it for dynamic resources, you might need create your own functions.
See also: Streaming mp4 files from PHP